1. Field of the Invention
The present invention relates to a contactless measuring system comprising at least one test probe forming part of a coupling structure for contactless decoupling of a signal running on a signal waveguide, wherein the signal waveguide is configured as a conductor track and as part of an electric circuit on a circuit board of the electrical circuit. The invention also relates to a calibration substrate for a contactless measuring system comprising at least one test probe forming part of a coupling structure for contactless decoupling of a signal running on a signal waveguide, wherein at least one calibration element, in particular a short-circuit standard, an open circuit standard, a resistance standard, or a conductor standard is provided on the calibration substrate, wherein the at least one calibration element is electrically connected to at least one signal waveguide, in particular a microstrip transmission line or a coplanar waveguide.
2. Description of Related Art
The determination of scattering parameters of electrical components embedded within a complex circuit by means of a contactless vector network analysis is known, for example from T. Zelder, H. Eul, “Contactless network analysis with improved dynamic range using diversity calibration”, Proceedings of the 36th European Microwave Conference, Manchester, UK, pages 478 to 481, September 2006 or T. Zelder, H. Rabe, H. Eul, “Contactless electromagnetic measuring system using conventional calibration algorithms to determine scattering parameters”, Advances in Radio Science—Kleinheubacher Berichte 2006, vol. 5, 2007. Compared with conventional contact-bound network analysis methods, the internal directional couplers of a network analyzer are replaced with contactless near field measuring probes which are directly connected to the vectorial measuring points of the analyzer. The measuring probes are positioned over the signal lines of the object being measured. The probes can act inductively and/or capacitively on the electromagnetic field of the planar conductor. In order to measure the scattering parameters, conventional calibration methods are used, such as are used for contact-bound network analysis.
In contactless vector network analysis, for each measuring port of an unknown test object (DUT—Device Under Test), at least one measuring probe, for example, a conductor loop or two capacitive probes are needed. It is known from, for example, F. De Groote, J. Verspecht, C. Tsironis, D. Barataud and J.-P. Teyssier, “An improved coupling method for time domain load-pull measurements”, European Microwave Conference, vol. 1, pages 4 ff., October 2005, to use contactless conductor loops made from coaxial semi-rigid lines. By contrast, it is known from T. Zelder, H. Eul, “Contactless network analysis with improved dynamic range using diversity calibration”, Proceedings of the 36th European Microwave Conference, Manchester, UK, pages 478 to 481, September 2006 or T. Zelder, H. Rabe, H. Eul, “Contactless electromagnetic measuring system using conventional calibration algorithms to determine scattering parameters”, Advances in Radio Science—Kleinheubacher Berichte 2006, vol. 5, 2007, to use exclusively capacitive probes in contactless measuring systems. From T. Zelder, I. Rolfes, H. Eul, “Contactless vector network analysis using diversity calibration with capacitive and inductive coupled probes”, Advances in Radio Science—Kleinheubacher Berichte 2006, vol. 5, 2007 and J. Stenarson, K. Yhland, C. Wingqvist, “An in-circuit noncontacting measurement method for S-parameters and power in planar circuits”, IEEE Transactions on Microwave Theory and Techniques, vol. 49, No. 12, pages 2567 to 2572, December 2001, measuring systems are known which are realized with a combination of capacitive and inductive probes.
Although contactless vector network analysis has the potential of characterizing components contactlessly, to date no contactless scattering parameter measurement of HF and microwave components embedded within a circuit has been performed. If measurements are to be made within a circuit, the positions of the contactless probes must be changed during and after the calibration. However, this implies a high level of complexity in order to reproduce the test probe positions during measurement of the calibration standard and of the test object, since the smallest deviations in the probe positioning lead to significant measuring errors.